The most general, and economical, method for preparing substituted amidines (B), (B') and (B") is from
(a) chloro(methylenammonium) chlorides (also called chloroformiminium chlorides), represented by formulae (A), (A'), and (A"), with primary amines ##STR1## and, (b) substituted imidoyl chlorides (C) with secondary or primary amines ##STR2## wherein R is a monovalent substituent selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, cycloalkenyl and heterocyclic radicals; R' and R" are monovalent organic radicals independently selected from the group consisting of alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, cycloalkenyl and heterocyclic radicals; and, Z is a divalent organic radical completing a 4 to 8 membered cycloaliphatic ring and containing (i) from 2 to 6 carbon atoms or (ii) from 2 to 6 carbon atoms and one hetero atom selected from the group consisting of oxygen, sulfur, and nitrogen with the proviso that no hetero atom is adjacent said nitrogen atom.
These processes are illustrated (a) in the book by P.A.S. Smith, Open Chain Nitrogen Compounds, Vol. 1, pp. 177-184 (1965), W. A. Benjamin, Inc., New York; (b) in the review article by R. L. Schriner and F. W. Neumann, in Chemical Reviews, Vol. 35, pp. 351-425 (1944); and in individual articles, such as (c) Chemistry and Industry, 1971, p. 175; and (d) Angewandte Chemie, Vol. 72, pp. 836-845 (1960). The yields, however, are only mediocre, usually between 40 and 70%, and drastic heating conditions (between 150.degree. and 180.degree. C.) are required to effect reactions with the more basic amines (as shown in reference (d), p. 839).